From 1966 to 2012 there were 90 public mass murders (4 or more victims) in the US according to researcher, Adam Lankford (2016).  Studying the characteristics of those that have committed mass murder in the past can help professionals develop interventions in vulnerable populations to reduce the risk of future mass murders and other types of violence. 

There are multiple categories and levels of severity of violence.  Each has specific characteristics.  However, there are some commonalities that could be used to assist people in getting the help they need before their interpersonal difficulties become severe and dangerous.

Someone that commits mass murder is generally a male that has had multiple problems for years.  He is often in his late teens through his forties.  He is marked by having the majority of the following 15 characteristics to a severe or chronic level and he also has few coping skills for everyday life stressors.  The more problems he has and the fewer the coping skills he has, the more likely it is that he will commit some type of violence in the future.  No one factor below automatically leads to violence.  It is the combination of the majority of these particular factors (and others not listed here).

Socially awkward or severely withdrawn
Narcissistic traits. My needs are the only ones that matter. 
Poor anger management with emotional outbursts
Mental Illness and/or Substance Abuse and not in treatment
Lack of empathy for others
Paranoia
Severe school or job difficulties, particularly in the arena of not getting along with authority or peers.
Violent communications.  Verbal threats of harm.
Major life stressors and losses such as loss of a primary relationship or job. 
An event that severely injures the ego or is seen as a narcissistic injury
The person has Average IQ or higher, but many emotional and interpersonal problems.
Depression, suicidal, or bipolar disorder
Severe difficulty with interpersonal relationships
Commits domestic violence
Extremely low frustration tolerance

These (and other) risk factors should be used in any assessment of future risk of violence and can be found on valid and reliable risk assessment tools such as the HCR-20, SARA, and the LS-RNR.  It is always important to use valid and reliable tools to the extent possible.  These assessment tools can be used when a person is disciplined at work or school for inappropriate interpersonal behavior leading to risk of being dismissed from the organization.  Such tools can also be used in investigations of terroristic threatening.  Behavioral health clinics and hospitals should use these tools when there is suspicion of future risk of violence. 

However, a meta analysis by Fazel, Singh, Doll, and Grann, (2012) indicates that risk tools at this stage in their development are better at eliminating those not at risk for committing violence.  Therefore, once it is determined that there is some level of risk for violence, a risk reduction plan for treatment and safety planning is recommended.  A risk reduction plan incorporates interventions to reduce the factors which are driving an individual’s risk for violence.   

For example, if one of the factors is mental illness or substance abuse, a referral for behavioral health services could be used.  Where there is reason to doubt compliance with the referral, and it is in conjunction with a legal, school, or work infraction, the intervention could be compulsory.  If the infraction is domestic violence, this can be a “red flag” indicator of risk for other kinds of community violence and can be used to mandate treatment to protect the partner, the children of the abusive adult, and the community.  A valid and reliable risk assessment tool and risk reduction plan should always be used in cases of domestic violence to determine treatment needed.  

Additionally, psycho-

Source: licensed from Adobe

Source: Licensed from Adobe

social treatments to reduce violent behaviors in forensic populations is different that interventions that may be used in non-forensic populations.   It may be more structured and aimed toward skill building.  Groups may be used more often.   Treatment for co-occurring disorders becomes more important, as well.  Structure, setting limits, and accountability are more important when working with those at risk for future violence, also.  Trauma informed care is essential with this population as many experienced childhood abuse and neglect.

In conclusion, the assessment and treatment for those at risk for violence is markedly different that that used for traditional behavioral health populations, even though those at risk can be treated by behavioral health providers.  This treatment can become an important preventative measure to reduce the level of violence in the US which is one of the highest among the industrialized nations of the world.  Once we understand how to recognize those at risk, providers can intervene in more effective ways to reduce the likelihood of future violence of all kinds including mass murder.